Despite extensive clinical, laboratory, and imaging evidence that the central nervous system (CNS) is persistently abnormal in some HIV-infected individuals with systemic viral suppression on combination antiretroviral therapy (cART), the underlying mechanisms of this perturbation are poorly understood, including etiologies, cells and tissues involved, and relation to potential persistence of HIV. In an era of increasing global access to cART, defining perturbations of the CNS on sustained cART and identifying potential interventions is the most salient neurologic issue for the 35 million people currently living worldwide with HIV. The current pilot project exploits recognition of the role of exosomal micro-RNAs (exo-miRNA) in disease pathogenesis to further our understanding of the processes underlying HIV related CNS abnormality detected on long-term suppressive cART. Exosomes are membrane nanovesicles released via exocytosis of donor cells that contain small non-coding miRNAs (exo-miRNAs) that regulate gene expression in target cells. Exo-miRNAs play important roles in disease pathogenesis including regulating immune responses in target tissues. Furthermore, viral exo- miRNAs may reveal HIV persistence, and other specific exo-miRNAs indicate cellular origins. To examine the associations between exo-miRNA in the CNS and cART treated HIV, in Aim 1 we will cross-sectionally profile exo-miRNA in cerebrospinal fluid (CSF) and blood by deep sequencing in individuals on sustained cART and HIV-uninfected comparison study participants. We hypothesize that CSF exo-miRNA associated with inflammation will be more abundant in cART-suppressed participants and that CSF exo-miRNAs will be enriched for inflammatory-mediating miRNAs compared to blood. We will explore whether HIV-derived exo-miRNAs can be detected in CSF, suggesting HIV persistence, and the impact of early versus later initiation of cART on exo-miRNA profiles. In Aim 2 we will investigate the mechanistic relationships between exo-miRNA profiles, immune activation and exhaustion in the CNS and blood, and neurocognitive performance. We hypothesize that in CSF and blood, exo-miRNAs linked to inflammation will correlate with activation of monocytes and T lymphocytes as measured by flow cytometry and soluble markers of immune activation, and that poorer neuropsychological testing performance will associate with inflammatory profiles of miRNA in CSF. Our long-term goal is to provide improved understanding of the causes of CNS perturbation in treated HIV in order to develop targeted adjunctive therapies to ameliorate HIV associated neurocognitive disorder.